Effect Of Nutrient Starvation Research Articles

DNA-PKcs is activated under nutrient starvation and activates Akt, MST1, FoxO3a, and NDR1

BackgroundPresence of unperfused regions containing cells under hypoxia and nutrient starvation; contributes to radioresistance in solid human tumors. We have previously reported that cultured cells; under nutrient starvation show resistance to ionizing radiation compare with cells under normal; condition, and that nutrient starvation increases ATM activity, which causes cellular resistance to; ionizing radiation (Murata et al., BBRC2018). For further investigation of molecular mechanisms; underlying radioresistance of cells under nutrient starvation, effects of nutrient starvation on activity; of DNA-PKcs have been investigated because both DNA-PKcs and ATM belong to the PIKK family; and are required for DNA DSBs repair. In addition to DNA-PKcs, effects of nutrient starvation on; activities of FoxO3a and its regulators Akt, MST1 and AMPK have been investigated because FoxO3a; mediates cellular responses to stress and is activated under nutrient starvation. MethodsA human glioblastoma cell line, T98G was used to examine the effects of nutrient starvation on activities and expression of DNA-PKcs, Akt, MST1, FoxO3a, NDR1, and AMPK. To elucidate; signal transduction pathways for FoxO3a activation under nutrient starvation, we examined effects of; specific inhibitors or siRNA for DNA-PKcs or Akt on activities and expression of MST1, FoxO3, NDR1, andAMPK. ResultsUnder nutrient starvation, phosphorylations of DNA-PKcs at Ser2056, Akt at Ser473, MST at Thr183, FoxO3a at Ser413, NDR1 at Ser281 and Thr282, and AMPK at Thr172 were increased, which suggests their activation. Nutrient starvation did not affect expression of DNA-PKcs, Akt, MST1, or NDR1, with decreased expression of FoxO3a and increased expression of AMPK. Inhibition; of DNA-PK suppressed phosphorylation of Akt under nutrient starvation. Inhibition of DNA-PK or; Akt suppressed phosphorylations of MST1, FoxO3a, and NDR1 under nutrient starvation, which; suggests DNA-PKcs and Akt activate MST1, FoxO3a, and NDR1. Inhibition of DNA-PK did not; suppress phosphorylation ofAMPK under nutrient starvation. ConclusionOur data suggest that DN-PKcs is activated under nutrient starvation and activates AktMST1, FoxO3a, and NDR1.

Knockdown of AMPKα decreases ATM expression and increases radiosensitivity under hypoxia and nutrient starvation in an SV40-transformed human fibroblast cell line, LM217

BackgroundPresence of unperfused regions containing cells under hypoxia and nutrient starvation contributes to radioresistance in solid human tumors. It is well known that hypoxia causes cellular radioresistance, but little is known about the effects of nutrient starvation on radiosensitivity. We have reported that nutrient starvation induced decrease of mTORC1 activity and decrease of radiosensitivity in an SV40-transformed human fibroblast cell line, LM217, and that nutrient starvation induced increase of mTORC1 activity and increase of radiosensitivity in human liver cancer cell lines, HepG2 and HuH6 (Murata et al., BBRC 2015). Knockdown of mTOR using small interfering RNA (siRNA) for mTOR suppressed radiosensitivity under nutrient starvation alone in HepG2 cells, which suggests that mTORC1 pathway regulates radiosensitivity under nutrient starvation alone. In the present study, effects of hypoxia and nutrient starvation on radiosensitivity were investigated using the same cell lines. MethodsLM217 and HepG2 cells were used to examine the effects of hypoxia and nutrient starvation on cellular radiosensitivity, mTORC1 pathway including AMPK, ATM, and HIF-1α, which are known as regulators of mTORC1 activity, and glycogen storage, which is induced by HIF-1 and HIF-2 under hypoxia and promotes cell survival. ResultsUnder hypoxia and nutrient starvation, AMPK activity and ATM expression were increased in LM217 cells and decreased in HepG2 cells compared with AMPK activity under nutrient starvation alone or ATM expression under hypoxia alone. Under hypoxia and nutrient starvation, radiosensitivity was decreased in LM217 cells and increased in HepG2 cells compared with radiosensitivity under hypoxia alone. Under hypoxia and nutrient starvation, knockdown of AMPK decreased ATM activity and increased radiation sensitivity in LM217 cells. In both cell lines, mTORC1 activity was decreased under hypoxia and nutrient starvation. Under hypoxia alone, knockdown of mTOR slightly increased ATM expression but did not affect radiosensitivity in LM217. Under hypoxia and nutrient starvation, HIF-1α expression was suppressed and glycogen storage was reduced. ConclusionOur data suggest that AMPK regulates ATM expression and partially regulates radiosensitivity under hypoxia and nutrient starvation. The molecular mechanism underlying the induction of ATM expression by AMPK remains to be elucidated.

Accumulation of lipid in <i>Dunaliella salina </i>under Nutrient Starvation Condition

The effect of nutrient starvation on lipid accumulation of Dunaliella salina A9 was studied. In nutrient starvation, cell colour changed from green to yellow (or orange) and cell growth reached stationary phase after 9 days of the culture. The study showed that under nutrient stress, decreased in cell growth is accompanied by carotenoid biosynthesis and lipid content of Dunaliella salina. The results of this study can be used to increase carotenoid and lipid production in microalgae for functional food and biofuel in the future.

Effect of nutrient starvation on proliferation and cytokine secretion of peripheral blood lymphocytes.

Proliferating cancer cells are exposed to nutrient deprivation. Numerous previous studies have demonstrated how nutrient deprivation affects cancer cells; however, immune cells exposed to the identical conditions have not been completely examined. Furthermore, T-helper 2 lymphocyte predominance in certain neoplastic diseases has been reported; however, the mechanism remains unclear. The present study aimed to confirm whether nutrient deprivation affected proliferation and cytokine secretion of peripheral blood lymphocytes (PBLs). The proliferation of PBLs from healthy donors, cultured in a medium containing various glucose levels, was assessed by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt (MTS) assay. The expression levels of interleukin (IL)-4 and interferon (IFN)-γ among CD4(+) T cells, cultured with or without glucose and activated with phorbol 12-myristate 13-acetate and ionomycin, were examined using an intracellular cytokine staining method. The proliferation of PBLs cultured in a medium containing <100 mg/dl glucose of the standard blood sugar (BS) level was significantly reduced compared with the proliferation observed in a medium containing a standard BS level or higher. PBLs cultured in a glucose-free medium contained a significantly higher percentage of IL-4-positive and a lower percentage of IFN-γ-positive CD4(+) T cells compared with those cultured in a high-glucose medium. Nutrient deprivation suppressed the proliferation of PBLs, fostered the secretion of IL-4 and reduced secretion of IFN-γ. It is therefore possible that glucose-deficient microenvironments in local cancer tissues cause a partial immunodeficiency, which is advantageous to cancer growth.

Effect of Nutrient Starvation under High Irradiance on Lipid and Starch Accumulation in Chlorella fusca (Chlorophyta)

The effect of nitrogen and sulphur limitation under high irradiance (PAR) was studied in the green microalga Chlorella fusca (Chlorophyta) in order to follow lipid and/or starch accumulation. Growth, biomass composition and the changes in photosynthetic activity (in vivo chlorophyll a fluorescence) were followed in the trials. The full nutrient culture showed high biomass production and starch accumulation at Day 1, when photosynthetic activity was high. Gradual deprivation (no nutrients added) became evident when photosynthesis was significantly suppressed (Day 3 onwards), which entailed a decrease of maximum relative electron transport rate (rETRmax) and increase of non-photochemical quenching (NPQ), accompanied by the onset of lipid accumulation and decline in starch content. In N- and S-starved cultures, rETRmax significantly decreased by Day 3, which caused a substantial drop in biomass production, cell number, biovolume and induction of lipid and starch accumulation. High starch content (45-50 % of DW) was found at the initial stage in full nutrient culture and at the stationary phase in nutrient-starved cultures. By the end of the trial, all treatments showed high lipid content (~30 % of DW). The full nutrient culture had higher biomass yield than starved treatments although starch (~0.2 g L(-1) day(-1)) and lipid (~0.15 g L(-1) day(-1) productivities were fairly similar in all the cultures. Our results showed that we could enrich biomass of C. fusca (% DW) in lipids using a two-stage strategy (a nutrient replete stage followed by gradual nutrient limitation) while under either procedure, N- or S-starvation, both high lipid and starch contents could be achieved.

Induction of a bZIP Type Transcription Factor and Amino Acid Catabolism-Related Genes in Soybean Seedling in Response to Starvation Stress

To address roles of bZIP transcription factors on regulation of amino acid catabolism under autophagy-induced plant cells, we examined the effect of nutrient starvation on the expression of low energy stress-related transcription factor homologs, GmbZIP53A and GmbZIP53B, and amino acid catabolism-related genes in soybean (Glycine max (L.) Merr.). Sucrose starvation treatment significantly enhanced the expressions of GmbZIP53A, but not GmbZIP53B asparagine synthase (GmASN1), proline dehydrogenase1 (GmProDH), and branched chain amino acid transaminase 3 (GmBCAT3). GmbZIP53-related immunoreactive signals were upregulated under severe starvation with sucrose starvation and protease inhibitors, while 3% sucrose and sucrose starvation had no or marginal effects on the signal. Profiles of induction of GmASN1, GmProDH and GmBCAT3 under various nutrient conditions were consistent with the profiles of GmbZIP53 protein levels but not with those of GmbZIP mRNA levels. These results indicate that GmbZIP53 proteins levels are regulated by posttranslational mechanism in response to severe starvation stress and that the increased protein of GmbZIP53 under severe starvation accelerates transcriptional induction of GmASN1, GmProDH, and GmBCAT3. Furthermore, it is conceivable that decrease of branched chain amino acid level by the BCAT-mediated degradation eventually enhances autophagy under severe starvation.

Effect of nutrient starvation on some aspects of nitrogen metabolism in substrate-grown strawberry plantings cv. Nyoho

Three-week nitrogen (N) supply restriction is a way to stimulate early and uniform flower induction in forced June-bearing nursery strawberry production in Japan. In the first weeks after planting into excessively-fertigated substrates, N-starved plantings undergo drastic changes in their N utilization and N metabolism, often facing symptoms of interveinal chlorosis in their young expanding leaves. Interveinal chlorosis is reflected in delayed plant development, and consequently in yield reduction. Characterizing variations in main parameters of N metabolism in plant tissues in N-fed and N-starved strawberry plantings cv. Nyoho, this report portrays the pattern of changes in N metabolism during the nursery period. Results show that foliar NH4-N and petiole NO3-N concentrations and N-assimilating enzymes activities in plant tissue were significantly reduced due to the N-starvation, making young plants unlikely to be adaptive to N rich nutrition after planting, and that subsequent NH4-N accumulation in plant tissues can lead to sever interveinal chlorosis.

Nutrient starvation effects on the allelochemical potency of Alexandrium tamarense (Dinophyceae)

Batch culture experiments were performed to investigate potential effects of nutrient starvation on the allelochemical potency of the toxic dinoflagellate Alexandrium tamarense. Triplicate cultures with reduced nitrate (−N) or phosphate (−P) seed were compared to nutrient-replete (+N+P) cultures. Total depletion of the dissolved inorganic limiting nutrient, reduced cell quotas, changed mass ratios of C/N/P and reduced cell yield clearly indicate that treatment cultures at stationary phase were starved by either N or P, whereas growth cessation of +N+P cultures was probably due to carbon limitation and/or a direct effect of high pH. Pulsed addition of the limiting nutrient allowed −N and −P cultures to resume growth. Lytic activity of A. tamarense as quantified by a Rhodomonas bioassay was generally high (EC50 around 100 cells mL−1) and was only slightly modulated by growth phase and/or nutrient starvation. Lytic activity per cell increased with time in both +N+P and −P cultures but not −N cultures. P-starved stationary-phase cells were slightly more lytic than +N+P cultures, but this difference may be due to increased cell size and/or accumulation of extracellular compounds. In conclusion, only slight changes but no general and major increase in lytic activity in response to nutrient starvation was observed.

Effect of nutrient starvation on the cellular composition and metabolic capacity of Saccharomyces cerevisiae.

This investigation addresses the following question: what are the important factors for maintenance of a high catabolic capacity under various starvation conditions? Saccharomyces cerevisiae was cultured in aerobic batch cultures, and during the diauxic shift cells were transferred and subjected to 24 h of starvation. The following conditions were used: carbon starvation, nitrogen starvation in the presence of glucose or ethanol, and both carbon starvation and nitrogen starvation. During the starvation period changes in biomass composition (including protein, carbohydrate, lipid, and nucleic acid contents), metabolic activity, sugar transport kinetics, and the levels of selected enzymes were recorded. Subsequent to the starvation period the remaining catabolic capacity was measured by addition of 50 mM glucose. The results showed that the glucose transport capacity is a key factor for maintenance of high metabolic capacity in many, but not all, cases. The results for cells starved of carbon, carbon and nitrogen, or nitrogen in the presence of glucose all indicated that the metabolic capacity was indeed controlled by the glucose transport ability, perhaps with some influence of hexokinase, phosphofructokinase, aldolase, and enolase levels. However, it was also demonstrated that there was no such correlation when nitrogen starvation occurred in the presence of ethanol instead of glucose.

Dual response to nutrients in Sorghum bicolor: The role of critical periods in expression of adaptive plasticity

The growth response of Sorghum bicolor was followed for 34 days for plants exposed to modified nutrient concentrations from day 8 (early-treated) and from day 12 (late-treated) following imbibition. In late-treated plants, the effect of nutrient starvation on growth rate increased with time. In contrast, the influence of nutrient starvation was not cumulative in early-treated plants, and the rate of growth was stabilized (with regard to plants growing in a standard medium) after about ten days of treatment. This suggests an adaptive adjustment of early-treated plants to low-nutrient concentration. Differences between early and late-treated plants suggest that expression of this adaptive response is possible only during a critical period in development, the same already identified for salt-adaptation in Sorghum. A similar relationship between shoot weight and blade length was observed for all the early-treated plants. This contrasts with the two relationships noticed for late-treated plants exposed to simi...

Improved survival of nutrient-starved cells of Rhizobium tropici CIAT899 in acid soil associated with high Al3+ and Mn2+ contents

The effect of nutrient starvation in Rhizobium tropici strain CIAT899 on stress resistance to Al3+ and Mn2+ and on survival in acid soil associated with high Al3+ and Mn2+ contents was examined. In the liquid culture medium, after starvation by the exhaustion of carbon, nitrogen, or phosphorus nutrients, CIAT899 survived at least 5 months with a slight loss of viability, indicating its ability to survive under starvation conditions. Upon re-suspension into a low phosphorus medium containing a high concentration of Al3+ (50 µM) or Mn2+ (500 µM), the carbon-starved cells showed an increased tolerance to Al3+ and Mn2+ compared with the non-starved cells. When inoculated to acid soils associated with high Al3+ and Mn2+ contents, the carbon-starved cells of CIAT899 showed an enhanced survival ability compared with the non-starved cells. These results suggest the advantage of the use of carbon-starved cells of Rhizobium as an inoculum to leguminous plants, especially in acid soil associated with high Al3+ and Mn2+ contents, in order to increase the nodulation by the inoculated strain through enhanced survival in soil.

In-line recording of PAM fluorescence of phytoplankton cultures as a new tool for studying effects of fluctuating nutrient supply on photosynthesis

Turbidostat cultures of Dunaliella salina (Chlorophyceae) and Thalassiosira weissflogii (Bacillariophyceae) were grown at fluctuating concentrations of nitrate, phosphate and silicate. In-line measurements of PAM fluorescence were used to monitor the effects of fluctuating nutrient supply on the photochemical efficiency of photosystem II reaction centres of light-adapted cells (ΔF/F′m). Besides the maximal photochemical efficiency of photosystem II reaction centres of dark-adapted cells (F v/F m), chlorophyll a, particulate organic carbon, nitrogen and phosphorus, and the cell number were measured frequently during the experiments. Following nutrient-replete growth, the cells were supplied with medium from which either nitrate, phosphate or silicate was omitted. When significant effects of nutrient starvation were indicated by the fluorescence parameters, a pulse of the deficient nutrient was added to the cultures. Our experimental set-up for in-line fluorescence measurements provided sensitive and reproducible detection of the various fluorescence signals, revealing strong influences of nutrient supply on the photochemical efficiency of photosystem II. In general the fluorescence values changed substantially within 1–30 min after re-addition of the deficient nutrient. Addition of phosphate and silicate induced an immediate characteristic decrease in fluorescence, whereas nitrate addition was characterized by a strong, delayed increase in fluorescence. Complete recovery to pre-starvation fluorescence values took about 48 h in all experiments. The physiological background of nutrient uptake is used to explain the observed tight couplings between fluorescence responses and nutrient re-addition. Our study clearly demonstrates that in-line fluorescence measurements provide a new tool for the investigation of phytoplankton reactions to fluctuating nutrients and offer the possibility to detect nutrient starvation in the field.

Effect of Nutrient Starvation on the Resistance of Escherichia coli O157:H7 to Subsequent Heat Stress

The resistance of three strains of Escherichia coli O157:H7 in their stationary growth phase to starvation (24 h in water at 37°C) followed by a heat treatment (56°C for up to 90 min) was determined. Starvation was found to increase significantly the resistance of two strains (NCTC 12079; eae+, VT1+, VT2+, and ATCC 43889 eae+, VT2+) but not the remaining strain (ATCC 43890 eae+, VT1+). Strain NCTC 12079 (only one tested) was shown to retain all of the three virulence factors after the two stresses. De novo protein synthesis was shown to be required for heat resistance. Evidence using an rpoS mutant indicated a central role for this gene in inducing heat resistance after a starvation stress. It is hoped that this work will contribute to more accurate risk assessments in certain food processing operations.

Histopathology ofScolytus ventralis(Coleoptera: Scolytidae) Infected bySulphuretylenchus elongatus(Nematoda: Sphaerulariidae)

Infection by the nematode Sulphuretylenchus elongatus (Massey) Nickle caused massive cellular necrosis in the internal organs of Scolytus ventralis LeConte, resulting in sterility, disruption of the digestive processes, and eventual death of the host. Cellular disintegration probably occurred through the secretion or excretion of toxins or the secretion of histolytic enzymes. Nematodes initially fed within the haemocoel, presumably on nutrients in the haemolymph, but invasion of the tissues was observed in the late stages of heavy infections. Sterility in females was induced at an earlier stage of infection and at lower nematode populations than in males. This phenomenon may have occurred through the direct effect of nutrient starvation on ovary development or through the effect of nutrient starvation and/or toxins on the endocrine control of ovary development.